This is a proposal to perform longitudinal studies on three already established population-based cohorts in areas exposed to 1) moderate levels of photochemical oxidant pollutants, 2) combined reductant, oxidant and hydrocarbon pollutants, 3) minimal levels of chemical pollutants, and a cohort to be established in an area chronically exposed to high levels of oxidant-type pollutants. The objects of the proposal are to 1) observe the natural history of chronic obstructive respiratory disease (CORD) and functional respiratory impairment, 2) identify environmental factors including chronic exposure to specific air pollutants which play a role in the evolution, exacerbation and rate of progression of CORD and/or functional impairment, 3) identify as yet unsuspected demographic, familial and constitutional characteristics of individuals who go on to develop irreversible CORD and/or functional impairment, 4) identify those parameters of expiratory flow, and the flow-volume curve derived from spirometry; the alveolar plateau, closing volume fraction and residual volume derived by the single-breath nitrogen test (SBNT); airway resistance, functional residual capacity, and specific conductants derived from body plethysmography; x-ray and reported symptoms which can best predict impending CORD and/or functional impairment at a still reversible stage in susceptible individuals, 5) provide information on the variability a) of individual performance and subgroup performance for each of these tests of lung function and b) associated with seasonal factors or other factors present at the time of testing. The more than 15,000 individuals in the cohorts who have been characterized by baseline lung function studies will be followed annually for reported changes in respiratory health, changes of address, etc. On the fifth anniversary of the baseline studies tests of lung function will be administered to members of the cohort. Variability will be evaluated by immediate retesting of a probability sample of individuals completing lung function at the Mobile Lung Function Laboratory, retesting a probability sample of individuals in the cohort at three-month intervals in each of the four seasons, and reexamining a probability sample of residents at the UCLA Pulmonary Function Laboratory using the same and more sophisticated tests of lung function.